U.S. patent application number 15/660099 was filed with the patent office on 2019-01-31 for fault mitigation for electrical actuator using regulated voltage control.
The applicant listed for this patent is GM Global Technology Operations LLC. Invention is credited to Xinyu Du, Yao Hu, Paul E. Krajewski, Joshua J. Sanchez.
Application Number | 20190036321 15/660099 |
Document ID | / |
Family ID | 65004286 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190036321 |
Kind Code |
A1 |
Hu; Yao ; et al. |
January 31, 2019 |
FAULT MITIGATION FOR ELECTRICAL ACTUATOR USING REGULATED VOLTAGE
CONTROL
Abstract
A method for mitigating an electrical actuator fault in a system
containing multiple actuators includes: applying multiple
predetermined conditions to each of multiple actuators in a vehicle
system to identify when at least one of the multiple actuators is
in a faulted condition; and increasing an input voltage to all of
the actuators to increase an output of the at least one of the
multiple actuators in the faulted condition to mitigate the faulted
condition.
Inventors: |
Hu; Yao; (Sterling Heights,
MI) ; Du; Xinyu; (Oakland Township, MI) ;
Sanchez; Joshua J.; (Sterling Heights, MI) ;
Krajewski; Paul E.; (Troy, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM Global Technology Operations LLC |
Detroit |
MI |
US |
|
|
Family ID: |
65004286 |
Appl. No.: |
15/660099 |
Filed: |
July 26, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D 41/221 20130101;
F02D 29/06 20130101; H02J 7/14 20130101; H02J 7/1461 20130101; H02H
9/045 20130101; H02J 7/0029 20130101; H02H 1/06 20130101; Y02T
10/40 20130101; B60R 16/03 20130101; F02D 41/3082 20130101 |
International
Class: |
H02H 1/06 20060101
H02H001/06; H02H 9/04 20060101 H02H009/04; B60R 16/03 20060101
B60R016/03 |
Claims
1. A method for mitigating an electrical actuator fault in a system
containing multiple actuators, comprising: applying multiple
predetermined conditions to each of multiple actuators in a vehicle
system to identify when at least one of the multiple actuators is
in a faulted condition; and increasing an input voltage to all of
the actuators to increase an output of the at least one of the
multiple actuators in the faulted condition to mitigate the faulted
condition.
2. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 1, further including
connecting each of the actuators to a vehicle generator operable
over a range of output voltages, wherein the increasing step
includes increasing an output voltage of the vehicle generator.
3. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 2, further including
determining a maximum available output voltage for the vehicle
generator prior to increasing the output voltage of the vehicle
generator.
4. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 3, further including
determining a safe voltage Vsafe for operating each of the multiple
actuators prior to increasing the output voltage of the vehicle
generator, wherein the safe voltage Vsafe is less than the maximum
available output voltage.
5. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 4, further including
limiting the input voltage to each of the actuators to the safe
voltage Vsafe.
6. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 3, further including
determining a safe voltage Vsafe for operating each of the multiple
actuators prior to increasing the output voltage of the vehicle
generator, wherein the safe voltage Vsafe is less than or equal to
the maximum available output voltage.
7. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 4, further including
prior to the increasing step calculating multiple correction
factors.
8. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 7, further including
prior to the increasing step applying a weighting factor to each of
the multiple correction factors.
9. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 8, further including
prior to the increasing step calculating an overall correction
factor Cf equaling a sum of the multiple correction factors
including the weighting factors plus 1.
10. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 7, further including:
prior to the increasing step calculating an adjusted voltage Vadj
defined as a minimum of [the maximum available output voltage of
the generator, the safe voltage Vsafe and a product of the overall
correction factor Cf and a present output voltage from the
generator]; and during the increasing step applying the adjusted
voltage Vadj as the input voltage.
11. A method for mitigating an electrical actuator fault in a
system containing multiple actuators, comprising: for each of
multiple actuators in a vehicle system calculating an actuator
output error .mu..sub.output.sub._.sub.err wherein the actuator
output error .mu..sub.output.sub._.sub.err is equivalent to a mean
of [an actuator desired output minus an actual output of the
actuator], a PWM duty cycle .mu..sub.pwm, and an adjusted PWM duty
cycle to define when a faulted condition of at least one of the
actuators is present; and increasing an input voltage to all of the
actuators to increase an output of the at least one of the multiple
actuators in the faulted condition to mitigate the faulted
condition.
12. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 11, further
including: calculating multiple conditions including a
Condition.sub.1, a Condition.sub.2, a Condition.sub.3, a
Condition.sub.4, and a Condition.sub.5; and determining if
Condition.sub.1 is true AND if any one or more of Condition.sub.2
OR Condition.sub.3 OR Condition.sub.4 OR Condition.sub.5 is also
true.
13. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 12, wherein
Condition.sub.1 defines (.mu..sub.output.sub._.sub.err greater than
a first threshold) AND (.mu..sub.pwm greater than a second
threshold) AND a fault diagnostics isolation result output defines
a projected actuator failure for at least one of the multiple
actuators.
14. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 13, wherein:
Condition.sub.2 defines a state of health of the actuator less than
a third threshold; Condition.sub.3 defines a long term correction
factor of the actuator greater than a fourth threshold;
Condition.sub.4 defines an adjusted PWM of the actuator greater
than a fifth threshold; and Condition.sub.5 defines an estimated
resistance of the actuator greater than a sixth threshold.
15. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 11, wherein the PWM
duty cycle .mu..sub.pwm of the at least one of the multiple
actuators in the faulted condition defines a mean PWM duty cycle
[.mu..sub.pwm=mean (PWM)].
16. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 11, wherein the
adjusted PWM duty cycle is calculated by multiplying a quotient of
a generator voltage divided by a desired output of each of the
actuators by a PWM duty cycle.
17. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 11, further including
prior to the increasing step: calculating multiple correction
factors including: a first correction factor
cf.sub.1=a.sub.1maximum of {0, or .mu..sub.output.sub._.sub.err-a
first threshold} a second correction factor cf.sub.2=a.sub.2maximum
of {0, or .mu..sub.pwm-a second threshold} a third correction
factor cf.sub.3=a.sub.3maximum of {0, or the third threshold minus
a state of health of the actuator} a fourth correction factor
cf.sub.4=a.sub.4maximum of {0, or a long term correction factor
minus a fourth threshold} a fifth correction factor
cf.sub.5=a.sub.5maximum of {0, or Adjusted PWM minus a fifth
threshold}; and a sixth correction factor cf.sub.6=a.sub.6maximum
of {0, or an estimated actuator resistance minus a sixth
threshold}; wherein a.sub.1, a.sub.2, a.sub.3, a.sub.4, a.sub.5,
a.sub.6 each define a scaling factor; calculating an overall
correction factor Cf using an equation Cf=1+[w.sub.1, w.sub.2,
w.sub.3, w.sub.4, w.sub.5,
w.sub.6][cf.sub.1+cf.sub.2+cf.sub.3+cf.sub.4+cf.sub.5+cf.sub.6]
wherein w.sub.1, w.sub.2, w.sub.3, w.sub.4, w.sub.5, w.sub.5,
w.sub.6 each define a weighting factor; and determining the input
voltage to apply as an adjusted voltage equal to [Cf multiplied by
a present voltage applied to the actuators].
18. A method for mitigating an electrical actuator fault in a
system containing multiple actuators, comprising: calculating an
actuator output error .mu..sub.output.sub._.sub.err, a PWM duty
cycle .mu..sub.pwm, and an adjusted PWM duty cycle for each of the
multiple actuators in the system; evaluating multiple conditions
for each of the actuators including a Condition.sub.1, a
Condition.sub.2, a Condition.sub.3, a Condition.sub.4, and a
Condition.sub.5, wherein a faulted condition of at least one of the
actuators is defined when Condition.sub.1 is true and at least one
of Condition.sub.2, or Condition.sub.3, or Condition.sub.4, or
Condition.sub.5 is true; determining a safe voltage Vsafe for
operating each of the multiple actuators connected to a vehicle
generator, when the safe voltage Vsafe is less than or equal to a
maximum available output voltage of a vehicle generator; and
increasing an output voltage of the vehicle generator to the safe
voltage Vsafe thereby increasing an output of the at least one of
the multiple actuators in the faulted condition to mitigate the
faulted condition.
19. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 18, further
including: identifying an overall correction factor; determining a
product of the overall correction factor and a voltage presently
applied to the actuators; and changing the output voltage to the
product prior to the increasing step if the product is less than
the safe voltage Vsafe.
20. The method for mitigating an electrical actuator fault in a
system containing multiple actuators of claim 19, further including
limiting the output voltage to the maximum available voltage of the
vehicle generator if the safe voltage Vsafe and the product are
each greater than the maximum available voltage.
Description
INTRODUCTION
[0001] The present disclosure relates to electrically controlled
actuators used in motor vehicles.
[0002] Electrically controlled actuators are used in many systems
of an automobile vehicle, including but not limited to fuel pumps,
camshafts, and the like. Many known actuators operate with
electrical motors controlled using a pulse width modulation
voltage. Actuator function may degrade over time due to various
conditions, including wear, temperature extremes including
overheating, and friction. As actuators degrade, known control
systems which sense a state of health (SOH) of the actuators may
attempt to compensate for reduced actuator output in several ways.
One such way is to increase the actuator output by increasing its
input to a predetermined maximum amount, for example by increasing
a fuel pump output pressure by applying a maximum pulse width
modulated (PWM) duty cycle of the pump. A further way is to
decrease the duty cycle of the pump by reducing or optimizing pump
operation when possible to extend pump life.
[0003] When degradation occurs resulting in an actuator fault,
known vehicle health management (VHM) systems do not provide fault
mitigation, but generally only provide a fault signal to the
vehicle operator and may generate a diagnostic code for use by a
maintenance technician or for remote transmission if the vehicle is
equipped with a telematics unit. This may undesirably result in a
"walk home" incident, wherein an actuator ceases to function at a
sufficient rate for sustaining proper operation of the engine or
transmission.
[0004] Thus, while current actuator control systems achieve their
intended purpose, there is a need for a new and improved actuator
fault mitigation system and method for actuator control during
fault conditions.
SUMMARY
[0005] According to several aspects, a method for mitigating an
electrical actuator fault in a system containing multiple actuators
includes: applying multiple predetermined conditions to each of
multiple actuators in a vehicle system to identify when at least
one of the multiple actuators is in a faulted condition; and
increasing an input voltage to all of the actuators to increase an
output of the at least one of the multiple actuators in the faulted
condition to mitigate the faulted condition.
[0006] In another aspect of the present disclosure, the method
further includes connecting each of the actuators to a vehicle
generator operable over a range of output voltages, wherein the
increasing step includes increasing an output voltage of the
vehicle generator.
[0007] In another aspect of the present disclosure, the method
further includes determining a maximum available output voltage for
the vehicle generator prior to increasing the output voltage of the
vehicle generator.
[0008] In another aspect of the present disclosure, the method
further includes determining a safe voltage Vsafe for operating
each of the multiple actuators prior to increasing the output
voltage of the vehicle generator, wherein the safe voltage Vsafe is
less than the maximum available output voltage.
[0009] In another aspect of the present disclosure, the method
further includes limiting the input voltage to each of the
actuators to the safe voltage Vsafe.
[0010] In another aspect of the present disclosure, the method
further includes determining a safe voltage Vsafe for operating
each of the multiple actuators prior to increasing the output
voltage of the vehicle generator, wherein the safe voltage Vsafe is
less than or equal to the maximum available output voltage.
[0011] In another aspect of the present disclosure, the method
further includes prior to the increasing step calculating multiple
correction factors.
[0012] In another aspect of the present disclosure, the method
further includes prior to the increasing step applying a weighting
factor to each of the multiple correction factors.
[0013] In another aspect of the present disclosure, the method
further includes prior to the increasing step calculating an
overall correction factor Cf equaling a sum of the multiple
correction factors including the weighting factors plus 1.
[0014] In another aspect of the present disclosure, the method
further includes prior to the increasing step calculating an
adjusted voltage Vadj idefined as a minimum of [the maximum
available output voltage of the generator, the safe voltage Vsafe
and a product of the overall correction factor Cf and a present
output voltage from the generator]; and during the increasing step
applying the adjusted voltage Vadj as the input voltage.
[0015] According to several aspects, a method for mitigating an
electrical actuator fault in a system containing multiple
actuators, comprising: for each of multiple actuators in a vehicle
system calculating an actuator output error
.mu..sub.output.sub._.sub.err wherein the actuator output error
.mu..sub.output.sub._.sub.err is equivalent to a mean of [an
actuator desired output minus an actual output of the actuator], a
PWM duty cycle .mu..sub.pwm, and an adjusted PWM duty cycle to
define when a faulted condition of at least one of the actuators is
present; and increasing an input voltage to all of the actuators to
increase an output of the at least one of the multiple actuators in
the faulted condition to mitigate the faulted condition.
[0016] In another aspect of the present disclosure, the method
further includes calculating multiple conditions including a
Condition.sub.1, a Condition.sub.2, a Condition.sub.3, a
Condition.sub.4, and a Condition.sub.5; and determining if
Condition.sub.1 is true AND if any one or more of Condition.sub.2
OR Condition.sub.3 OR Condition.sub.4 OR Condition.sub.5 is also
true.
[0017] In another aspect of the present disclosure, Condition.sub.1
defines (.mu..sub.output.sub._.sub.err greater than a first
threshold) AND (.mu..sub.pwm greater than a second threshold) AND a
fault diagnostics isolation result output defines a projected
actuator failure for at least one of the multiple actuators.
[0018] In another aspect of the present disclosure, Condition.sub.2
defines a state of health of the actuator less than a third
threshold; Condition.sub.3 defines a long term correction factor of
the actuator greater than a fourth threshold; Condition.sub.4
defines an adjusted PWM of the actuator greater than a fifth
threshold; and Conditions defines an estimated resistance of the
actuator greater than a sixth threshold.
[0019] In another aspect of the present disclosure, the PWM duty
cycle .mu..sub.pwm of the at least one of the multiple actuators in
the faulted condition defines a mean PWM duty cycle
[.mu..sub.pwm=mean (PWM)].
[0020] In another aspect of the present disclosure, the adjusted
PWM duty cycle is calculated by multiplying a quotient of a
generator voltage divided by a desired output of each of the
actuators by a PWM duty cycle.
[0021] In another aspect of the present disclosure, the method
further includes prior to the increasing step: calculating multiple
correction factors including: a first correction factor
cf.sub.1=a.sub.1maximum of {0, or .mu..sub.output.sub._.sub.err-a
first threshold}; a second correction factor
cf.sub.2=a.sub.2maximum of {0, or .mu..sub.pwm-a second threshold};
a third correction factor cf.sub.3=a.sub.3maximum of {0, or the
third threshold minus a state of health of the actuator}; a fourth
correction factor cf.sub.4=a.sub.4maximum of {0, or a long term
correction factor minus a fourth threshold}; a fifth correction
factor cf.sub.5=a.sub.5maximum of {0, or Adjusted PWM minus a fifth
threshold}; and a sixth correction factor cf.sub.6=a.sub.6maximum
of {0, or an estimated actuator resistance minus a sixth
threshold}; wherein a.sub.1, a.sub.2, a.sub.3, a.sub.4, a.sub.5, as
each define a scaling factor; calculating an overall correction
factor Cf using an equation Cf=1+[w.sub.1, w.sub.2, w.sub.3,
w.sub.4, w.sub.5,
w.sub.6][cf.sub.1+cf.sub.2+cf.sub.3+cf.sub.4+cf.sub.5+cf.sub.6]
wherein w.sub.1, w.sub.2, w.sub.3, w.sub.4, w.sub.5, w.sub.6 each
define a weighting factor; and determining the input voltage to
apply as an adjusted voltage equal to [Cf multiplied by a present
voltage applied to the actuators].
[0022] According to several aspects, a method for mitigating an
electrical actuator fault in a system containing multiple
actuators, includes: calculating an actuator output error
.mu..sub.output.sub.--err, a PWM duty cycle .mu..sub.pwm, and an
adjusted PWM duty cycle for each of the multiple actuators in the
system; evaluating multiple conditions for each of the actuators
including a Condition.sub.1, a Condition.sub.2, a Condition.sub.3,
a Condition.sub.4, and a Condition.sub.5, wherein a faulted
condition of at least one of the actuators is defined when
Condition.sub.1 is true and at least one of Condition.sub.2, or
Condition.sub.3, or Condition.sub.4, or Condition.sub.5 is true;
determining a safe voltage Vsafe for operating each of the multiple
actuators connected to a vehicle generator, when the safe voltage
Vsafe is less than or equal to a maximum available output voltage
of a vehicle generator; and increasing an output voltage of the
vehicle generator to the safe voltage Vsafe thereby increasing an
output of the at least one of the multiple actuators in the faulted
condition to mitigate the faulted condition.
[0023] In another aspect of the present disclosure, the method
further includes identifying an overall correction factor;
determining a product of the overall correction factor and a
voltage presently applied to the actuators; and changing the output
voltage to the product prior to the increasing step if the product
is less than the safe voltage Vsafe.
[0024] In another aspect of the present disclosure, the method
further includes limiting the output voltage to the maximum
available voltage of the vehicle generator if the safe voltage
Vsafe and the product are each greater than the maximum available
voltage.
[0025] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0027] FIG. 1 is a schematic illustration of a vehicle system
having fault mitigation for electrical actuators using regulated
voltage control according to an exemplary embodiment;
[0028] FIG. 2 is a graph of an exemplary actuator pump operation
during normal and faulted conditions;
[0029] FIG. 3 is a graph comparing output from each of a faulted
pump and a normally functioning pump at varying input voltage
levels; and
[0030] FIG. 4 is a flow diagram describing a method for determining
an adjusted input voltage to provide fault mitigation for
electrical actuators using regulated voltage control for the system
of FIG. 1.
DETAILED DESCRIPTION
[0031] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0032] Referring to the Figures in general, wherein like reference
numbers correspond to like or similar components throughout the
several figures, and referring specifically to FIG. 1, a vehicle 10
includes an internal combustion engine 12 providing motive force to
a transmission 14 having an input member 16 and an output member
18. The engine 12 may be selectively connected to the transmission
14 using an input clutch and damper assembly 20. The vehicle 10 may
also include a DC energy storage system 22, e.g., a rechargeable
battery, which may be electrically connected to provide starting
current to the engine 12, or to provide power if the vehicle 10 is
a hybrid electric vehicle (HEV). Output torque from the
transmission 14 is ultimately transferred via the output member 18
to a set of driven wheels 24 to propel the vehicle 10.
[0033] Vehicle 10 further includes a fuel tank 26 containing a
supply of fuel 28 such as gasoline, ethanol, E85, or other
combustible fuel sealed relative to the surrounding environment.
Vehicle 10 also includes multiple actuators, which according to one
aspect include a fuel pump 30 such as a roller cell pump or a
gerotor pump which may be submerged in the fuel 28 within the fuel
tank 26, and is operable for circulating the fuel 28 to the
internal combustion engine 12 in response to control and feedback
signals (arrow 32) from a controller 34. For simplicity, fuel rails
and injectors of the engine 12 and actuators which for exemplary
control functions of one or more engine camshafts, which define
further actuators of the vehicle 10 are omitted from FIG. 1.
[0034] Vehicle 10 further includes a control system 36 in
communication with a generator 38 which can provide a variable
voltage. The control system 36 is also in communication with
multiple actuators 40, 42, 44, 46 in addition to the exemplary
electrical fuel pump 30. The controller 34 is configured for
providing operational control signals to the various actuators,
determining a state of health (SOH) term for each of the various
actuators including the fuel pump 30 in the control system 36, and
for determining if a fault condition of one or more of the
actuators is present. Following the determination that a fault
condition is present, the controller 34 is further configured for
calculating an upper bound of a safe generator voltage Vsafe 48,
and for calculating an increased generator voltage Vincr 50 that
can be safely applied to all of the actuators, including the fuel
pump 30, to maximize an operating output of the actuator presently
operating in a fault condition to mitigate the fault condition.
[0035] Referring to FIG. 2 and again to FIG. 1, an exemplary fault
condition for one of the actuators is presented in relation to the
fuel pump 30. FIG. 2 presents a graph 52 including a fuel pump
power module output PWM duty cycle 54 expressed as a percentage of
the PWM duty cycle over a time line 56. As known, PWM defines a
pulse width modulated voltage or signal and a PWM duty cycle
defines the control signal for most commonly used actuators. In a
first curve portion 58, a normally operating fuel pump duty cycle
ranges between approximately 25% up to 43%. Beginning at an
exemplary date of approximately October 13, a second curve portion
60 for the fuel pump 30 presents a degrading and therefore a
faulted condition for the fuel pump power module output PWM duty
cycle which reaches a maximum duty cycle of 100% at approximately
October 19. The fuel pump 30 is repaired on or about November 21,
as indicated by a vertical line 62, therefore as shown in a third
curve portion 64 for the fuel pump 30 the fuel pump power module
output PWM duty cycle returns to a normal operation ranging between
approximately 25% up to 45%.
[0036] The PWM duty cycle can normally be determined using the
following proportionality equation:
PWM .varies. Desired Output Generator Voltage .times. Actuator SOH
.times. [ 1 + a ( Desired Output - Actual Output ) ]
##EQU00001##
Using for the present example the fuel pump 30 as one of the
multiple system actuators, as degradation of the actuator or pump
occurs, in order to continue to meet the demanded output from the
fuel pump 30, feed-back control from the fuel pump 30 is applied to
determine a higher PWM duty cycle in order to satisfy pump demand,
however, pump operation is limited to the maximum 100% PWM duty
cycle using 100% of the available power. In an exemplary aspect of
the present disclosure, using the second curve portion 60 it is
desirable to identify when a fuel pump power module output PWM duty
cycle percentage indicates the faulted condition of the fuel pump
30 has been reached. This may be at a predetermined PWM duty cycle
percentage such as at 50% when the PWM duty cycle has exceeded its
normal high value of approximately 45%. Once the faulted condition
has been reached, an algorithm of the present disclosure calculates
corrective mitigating action to permit the fuel pump 30 to continue
to achieve as close to its maximum output pressure as possible.
[0037] Referring to FIG. 3 and again to FIG. 2, a graph 66 presents
operational curves comparing a pump output pressure 68 versus an
input voltage multiplied by the PWM duty cycle 70 applied to the
fuel pump 30 for each of a new or nominal operational pump curve 72
and a degraded pump curve 74. It is evident that at lower input
voltage, for example at an input voltage 76 normally applied to
obtain maximum vehicle fuel economy, a pump output pressure 78 of
the degraded pump curve 74 is more than 100 kpa below a maximum
pump output pressure 80 of the nominal operational pump curve
72.
[0038] When the input voltage is increased, for example to an input
voltage 82, a pump output pressure 84 of the degraded pump curve 74
is increased and is substantially equal to a pump output pressure
86 of the nominal operational pump curve 72. It is evident from
FIG. 3 that increasing the input voltage of a degrading or faulted
pump, or other actuator, can at least temporarily increase an
output of a degrading or faulted pump or actuator up to an output
of a nominally operating actuator. It is also true however that
increasing the output voltage of the generator 38 will equally
increase the input voltage to all of the actuators of the vehicle
10. It is therefore necessary prior to inducing a global voltage
increase to identify a safe input voltage for each of the actuators
due to the varied operational parameters, heat loading, and the
like of each actuator.
[0039] Referring to FIG. 4, multiple process steps are provided
which identify the safe generator voltage Vsafe 48 that can be
applied to all of the system actuators if any one or more of the
system actuators is operating in a fault condition. The applied
safe generator voltage Vsafe 48 will then act to increase the
output of all of the actuators, including the faulted actuator,
thereby mitigating the fault condition without inducing a walk home
scenario for the vehicle 10.
[0040] In a first step 88, multiple actuator values are calculated
to identify if an actuator is defined as being in a faulted
condition. In a first calculated actuator value an actuator output
error .mu..sub.output.sub._.sub.err is equivalent to the mean of an
actuator desired output (such as a new pump output pressure) minus
an actual output (such as an existing pump output pressure) of the
actuator [.mu..sub.output.sub._.sub.err=mean (Desired Output-Actual
Output)]. In a second calculated value a PWM duty cycle of the
actuator .mu..sub.pwm is determined as a mean PWM duty cycle
[.mu..sub.pwm=mean (PWM)]. A normalized or adjusted PWM duty cycle
is calculated to identify a level of degradation by applying a
constant k.sub.1 using the equation:
Adjusted PWM = k 1 Generator Voltage Desired Output PWM
##EQU00002##
where the generator voltage is a measured output voltage of the
vehicle generator, the desired output defines an actuator output
using a new or nominal actuator, and adjusted PWM defines a mean
pulse width modulation duty cycle of the actuator.
[0041] In a second step 90, based on the above calculations, the
following five predetermined conditions are applied as defined
below to identify a state of health of each of the system
actuators, to thereby identify if any of the actuators is degraded
or faulted: [0042] Condition.sub.1:
(.mu..sub.output.sub._.sub.err>Thrd.sub.1) AND
(.mu..sub.pwm>Thrd.sub.2) AND (fault diagnostics/isolation
results=actuator failure); [0043] Condition.sub.2:
SOH<Thrd.sub.3 where SOH defines a state of health term of the
suspected faulted actuator; [0044] Condition.sub.3:
LTCF>Thrd.sub.4 where LTCF defines a long term correction
factor; [0045] Condition.sub.4: Adjusted PWM>Thrd.sub.5 based on
the adjusted PWM calculated above; [0046] Condition.sub.5:
Estimated Resistance>Thrd.sub.6, where the estimated resistance
defines a measured or estimated internal resistance of the
suspected faulted actuator. [0047] In the above conditions
Thrd.sub.1, Thrd.sub.2, Thrd.sub.3, Thrd.sub.4, and Thrd.sub.5 are
predetermined thresholds which may vary between individual vehicle
designs or between individual vehicles based on initial performance
testing. The term fault diagnostics/isolation results=actuator
failure in above Condition.sub.1 is a diagnostic signal created
using system fault diagnostics generated when one of the multiple
actuators is predicted to fail. In the second step 90 applying the
above conditions, any one of the multiple vehicle actuators is
defined as being in a faulted condition if Condition.sub.1 is true
AND if any one or more of Condition.sub.2 OR Condition.sub.3 OR
Condition.sub.4 OR Condition.sub.5 is also true for that actuator.
If any input associated with Condition.sub.2, Condition.sub.3,
Condition.sub.4 or Condition.sub.5 is not available, then that
condition is ignored.
[0048] In a third step 92, if the output from the second step 90 is
YES, wherein Condition.sub.1 is true AND if any one or more of
Condition.sub.2 OR Condition.sub.3 OR Condition.sub.4 OR
Condition.sub.5 is also true, the actuator is considered faulted
and up to six independent correction factors are then determined to
weight the effect of each of the condition terms. The correction
factors are determined as follows:
cf.sub.1=a.sub.1maximum of {0, or
.mu..sub.output.sub._.sub.err-Thrd.sub.1}
cf.sub.2=a.sub.2maximum of {0, or .mu..sub.pwm-Thrd.sub.2}
cf.sub.3=a.sub.3maximum of {0, or Thrd.sub.3-SOH}
cf.sub.4=a.sub.4maximum of {0, or LTCF-Thrd.sub.4}
cf.sub.5=a.sub.5maximum of {0, or Adjusted PWM-Thrd.sub.5}
cf.sub.6=a.sub.6maximum of {0, or Estimated
Resistance-Thrd.sub.6}
By applying a maximum of either zero or the following term in the
above correction factors, the correction factor will always be
either zero or have a positive value. If any input associated with
cf1, cf2, cf3, cf4, cf5, cf6, is not available, then that
correction factor is ignored.
[0049] In determining the above correction factors, the terms are
not equivalent. For example the PWM duty cycle ranges from zero to
100, while the mean output pressure from an actuator in kpA may
range in the hundreds. For this reason, the overall correction
factor Cf can also be adjusted to normalize a scale of the
individual correction factor terms using a scaling factor.
Predetermined scaling factors a.sub.1, a.sub.2, a.sub.3, a.sub.4,
a.sub.5, a.sub.6 may therefore be applied to any or all of the
correction factors.
[0050] In a fourth step 94, an overall correction factor Cf is
determined using the following equation:
Cf=1+[w.sub.1, w.sub.2, w.sub.3, w.sub.4, w.sub.5,
w.sub.6][cf.sub.1+cf.sub.2+cf.sub.3+cf.sub.4+cf.sub.5+cf.sub.6].sup.T
where w.sub.1, w.sub.2, w.sub.3, w.sub.4, w.sub.5, w.sub.6 each
define a weighting factor which can be assigned to each correction
factor based on its importance. For example, if an actuator does
not include the LTCF term its weighting factor w.sub.4 would equal
zero thereby nullifying the correction factor cf.sub.4. The
weighting factors will be retained for each calculation, but may
vary between different vehicle models and may vary from one vehicle
to another for the same vehicle model. The weighting factors may be
determined during an initial calibration of the vehicle, and may
vary if one of the calibration factors is deemed to have greater
importance than another.
[0051] In a fifth step 96, when it is desirable to increase the
generator output voltage to mitigate a faulted actuator, an upper
bound of the safe generator voltage Vsafe 48 incorporating safety
criteria is first determined based on the status of each of the
actuators. Vsafe 48 defines a maximum generator output voltage
above a measured present or original generator output voltage that
can be set which is safe to apply to of each of the system
actuators, not just to the faulted actuator. For example, if one of
the actuators has a high resistance fault it can tolerate a lower
input voltage due to actuator overheat concerns, and the converse
is true.
[0052] In a sixth step 98, an adjusted generator voltage Vadj is
then calculated using the following equation:
Vadj=minimum of {V.sub.max, OR V.sub.safe, OR cfV.sub.original}
where V.sub.max defines a maximum achievable output voltage of the
generator saved in a memory, V.sub.safe 48 is calculated as noted
above in the fifth step 96, and CfV.sub.original is the original or
presently applied generator output voltage multiplied by the
overall correction factor Cf calculated in the fourth step 94
above. A control signal is then sent to the generator 38 to
increase an output voltage of the generator 38 up to the adjusted
generator voltage Vadj.
[0053] In a seventh step 100, if the output from the second step 90
is NO, wherein either Condition.sub.1 is false OR if
Condition.sub.1 is true but each of Condition.sub.2 AND
Condition.sub.3 AND Condition.sub.4 AND Condition.sub.5 is false
the overall correction factor Cf from the above equation
Cf=1+[w.sub.1, w.sub.2, w.sub.3, w.sub.4, w.sub.5,
w.sub.6][cf.sub.1+cf.sub.2+cf.sub.3+cf.sub.4+cf.sub.5+cf.sub.6].sup.T
is equal to one. The cfV.sub.original term therefore controls and
the original or presently applied voltage V.sub.original will be
retained.
[0054] A system and method for mitigating an electrical actuator
fault in a system containing multiple actuators of the present
disclosure offers several advantages. These include means to
identify when an actuator has reached a faulted condition, and a
process to identify a voltage increase that the vehicle generator
can output that is safe to apply to all of the system actuators
that simultaneously increases an output of the faulted actuator.
This permits near normal continued operation of the vehicle until
corrective action can be taken for the faulted actuator.
[0055] The description of the present disclosure is merely
exemplary in nature and variations that do not depart from the gist
of the present disclosure are intended to be within the scope of
the present disclosure. Such variations are not to be regarded as a
departure from the spirit and scope of the present disclosure.
* * * * *